1、什么是膠合板？

膠合板(ban)(ban)(ban)(ban)是一種人造(zao)板(ban)(ban)(ban)(ban)，是將原木沿(yan)年輪方向旋切成大張單(dan)板(ban)(ban)(ban)(ban)，經干燥、涂膠后按(an)相鄰(lin)單(dan)板(ban)(ban)(ban)(ban)層(ceng)木紋(wen)方向相互垂直的(de)原則組坯(pi)、膠合而成的(de)板(ban)(ban)(ban)(ban)材。單(dan)板(ban)(ban)(ban)(ban)層(ceng)數為(wei)奇數，一般為(wei)三(san)層(ceng)至十三(san)層(ceng)，常(chang)見的(de)有三(san)合板(ban)(ban)(ban)(ban)、五合板(ban)(ban)(ban)(ban)、九(jiu)合板(ban)(ban)(ban)(ban)、和十三(san)合板(ban)(ban)(ban)(ban)（市場上俗稱(cheng)為(wei)三(san)厘(li)板(ban)(ban)(ban)(ban)，五厘(li)板(ban)(ban)(ban)(ban)，九(jiu)厘(li)板(ban)(ban)(ban)(ban)，十三(san)厘(li)板(ban)(ban)(ban)(ban)）。外層(ceng)的(de)正面(mian)(mian)單(dan)板(ban)(ban)(ban)(ban)稱(cheng)為(wei)面(mian)(mian)板(ban)(ban)(ban)(ban)，反面(mian)(mian)的(de)稱(cheng)為(wei)背板(ban)(ban)(ban)(ban)，內層(ceng)板(ban)(ban)(ban)(ban)稱(cheng)為(wei)芯(xin)板(ban)(ban)(ban)(ban)。

2、分類：

一類(lei)膠(jiao)合板為耐(nai)氣候、耐(nai)沸水(shui)膠(jiao)合板，由此及(ji)彼有耐(nai)久、耐(nai)高溫(wen)，能(neng)蒸汽處(chu)理的(de)優點；

二類膠合(he)板(ban)為耐水(shui)膠合(he)板(ban)，能(neng)在(zai)冷水(shui)中浸(jin)漬和(he)短時(shi)間熱水(shui)浸(jin)漬；

三類(lei)膠合板為耐潮(chao)膠合板，能在(zai)冷(leng)水中短時(shi)間(jian)浸漬，適于(yu)室內常溫下使用(yong)。用(yong)于(yu)家具和一般建筑(zhu)用(yong)途；

四類合(he)板為不耐潮(chao)膠(jiao)合(he)板，在室(shi)內常(chang)態下使(shi)用，一般用途膠(jiao)合(he)板用材有(you)櫸(ju)木、椴木、水曲柳(liu)、樺木、榆(yu)木、楊木等。

3、對稱原則：

對(dui)稱中(zhong)(zhong)(zhong)心平面(mian)(mian)兩(liang)側的單(dan)(dan)(dan)板(ban)，無論樹種，單(dan)(dan)(dan)板(ban)厚度、層數、制造(zao)方(fang)(fang)法(fa)、纖維方(fang)(fang)向(xiang)和(he)單(dan)(dan)(dan)板(ban)的含水(shui)率都應該互(hu)相對(dui)應，即(ji)對(dui)稱原則。膠(jiao)合板(ban)中(zhong)(zhong)(zhong)心平面(mian)(mian)兩(liang)側各對(dui)應層不(bu)(bu)同方(fang)(fang)向(xiang)的應力大小相等。因此，當膠(jiao)合板(ban)含水(shui)率變(bian)化時，其結構穩定，不(bu)(bu)會(hui)產生變(bian)形，開裂(lie)等缺陷(xian)；反之，如果對(dui)稱中(zhong)(zhong)(zhong)心平面(mian)(mian)兩(liang)側對(dui)應層有某些差異，將會(hui)使(shi)(shi)對(dui)稱中(zhong)(zhong)(zhong)心平面(mian)(mian)兩(liang)側單(dan)(dan)(dan)板(ban)的應力不(bu)(bu)相等，使(shi)(shi)膠(jiao)合板(ban)產生變(bian)形、開裂(lie)。

4、奇數層原則：

由(you)于膠(jiao)(jiao)合板(ban)的(de)(de)結構(gou)是相鄰(lin)層(ceng)(ceng)(ceng)單(dan)板(ban)的(de)(de)纖維方向(xiang)互相垂，又必須符合對稱(cheng)原則，因(yin)此它的(de)(de)總(zong)層(ceng)(ceng)(ceng)數(shu)必定是奇(qi)(qi)數(shu)。如：三層(ceng)(ceng)(ceng)板(ban)、五層(ceng)(ceng)(ceng)板(ban)、七層(ceng)(ceng)(ceng)板(ban)等。奇(qi)(qi)數(shu)層(ceng)(ceng)(ceng)膠(jiao)(jiao)合板(ban)彎曲(qu)時(shi)(shi)大(da)的(de)(de)水平剪應(ying)(ying)力作(zuo)用(yong)在中心單(dan)板(ban)上，使其有(you)較大(da)的(de)(de)強度(du)。偶數(shu)層(ceng)(ceng)(ceng)膠(jiao)(jiao)合板(ban)彎曲(qu)時(shi)(shi)大(da)的(de)(de)水平剪應(ying)(ying)力作(zuo)用(yong)在膠(jiao)(jiao)層(ceng)(ceng)(ceng)上而(er)不是作(zuo)用(yong)在單(dan)板(ban)上，易使膠(jiao)(jiao)層(ceng)(ceng)(ceng)破壞，降低(di)了膠(jiao)(jiao)合板(ban)強度(du)。